What is the time and space complexity of Implement Object.is()?

Time complexity: O(1). Space complexity: O(1).

Implement Object.is()

Easy

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Solution Guide: Implement Object.is()

Approach

Handle the two edge cases where === gives incorrect results: NaN should equal NaN (use Number.isNaN to detect both), and -0 should not equal +0 (use 1/x to distinguish via Infinity signs). For all other values, fall through to strict equality.

Complexity Analysis

Time: O(1)
Space: O(1)

Pattern

Same-Value Equality

Why It Works

The 1/x trick exploits the fact that 1/+0 is Infinity while 1/-0 is -Infinity, distinguishing the two zeros that === considers equal. Number.isNaN correctly identifies NaN which === rejects.

Updated Feb 2026